Multidrug-resistance proteins and drug-efflux pumps have been characterized in many organisms, and they represent a widely used mechanism of drug resistance. In a recent issue of Antimicrobial Agents and Chemotherapy (April 2005), investigators report results from a study of efflux pumps in Helicobacter pylori. The genome of H pylori 26695 contains 27 translocases, among which are HP1184, which is similar to other well-characterized multidrug-resistance translocases, and 4 other translocases (HP0605, HP0971, HP1327, and HP1489), which are similar to outer membrane TolC proteins. Investigators performed gene knockout experiments and assessed the bacteria now lacking these proteins for susceptibility to antibiotic and toxic compounds. The HP0605 knockout mutant demonstrated increased susceptibility to novobiocin and sodium deoxycholate, and a double knockout of HP0605 and HP0971 had increased susceptibility to metronidazole.